It's that unique gene pool that brought neurologist and geneticist Kari Stefansson home after 20 years abroad.

"When you begin to look at genetics, when you begin to think about life in general, it turns out all life on Earth is rooted in DNA," Stefansson said. "There is no life on Earth that is not based on information that lies in this miraculous macromolecule that we call DNA."

Stefansson returned home to Iceland two decades ago and founded a company called deCODE, with the ambitious goal of mapping the genome of the entire country. It would be a challenge but not impossible, as in 2016, Iceland's population totaled roughly 332,000 people.

"We claim that we can sequence the whole genomes for very large numbers of people," Stefansson told CNN's Dr. Sanjay Gupta at deCODE headquarters in Reykjavik. "For example, in this building, we have sequenced the whole genomes of 40,000 people. But that claim is not completely authentic. It's a little bit false, because, yes, we have sequenced it down to an individual basis, but there are certain features in the sequence we have yet to figure out."

The missing piece that fascinates Stefansson the most is the brain.

He says it is the one organ we don't completely understand. But for him, the key to everything lies in our genetics.

Preventing Alzheimer's disease

A genome is our entire set of DNA, the chemical compound that contains genetic instructions. It is the code that tells our bodies how to function, from our organs right down to our cells.

Ultimately, it is 6 billion pieces of data, arranged in 3 billion base pairs, making up hundreds of thousands of genes.

When correlated against medical records accessed through the government the team can identify changes linked to a disease.

Stefansson's team at deCODE has identified genes that impact the chances of developing conditions such as Alzheimer's, heart disease and breast cancer. They have even brought it to a level of problem-solving and creativity. Scientists at deCODE can tell you, based on your genetic makeup, whether you like crossword puzzles or have an artistic mind.

"Human genetics is the study of human diversity," Stefansson said. "And what you are trying to do is to figure out how information lies in the genome that has an impact on human diversity. And having, for example, the genealogy gives you the avenue by which this information is passed from one generation to the next."

The genealogy, or family history, is the other piece that brought Stefansson home to work on this project.

Most Icelanders can trace their lineage to a single Viking settler. Armed with that information, deCODE can track disease trends through family trees. So when researchers find a gene mutation or variant, it is easier to trace.

Iceland's population has remained relatively cut off from the rest of the world.

"We discovered a variant a few years back, maybe three or four years back, that confers protection against Alzheimer's disease," Stefansson explained. "It's a rare (gene) variance found in about 1% of the Icelandic population, and if you carry that variant, you are almost completely protected against Alzheimer's disease."

However, variants identified in the homogenous Icelandic population may not prove to be effective options among a more heterogeneous population.

The next step is to replicate what the genetic variant does in the body, in the form of medicine, to protect the health of others. That's where deCODE's parent company, the biopharmaceutical company Amgen, comes in. Amgen purchased the project in 2012.

While deCODE publishes all its scientific findings, Amgen is getting a head start using the information.

Sean Harper, head of research and development at Amgen, says the key for the company -- or for any company making drugs based off genetic information -- is the knowledge that it works in humans, unlike starting with animals.

"We start our work with the certainty that the target we're going after is actually relevant in humans in the path of physiology of the disease," Harper said. "That's what the genetics is telling you. What's amazing about the human genetics is, they can actually establish causality of the link of these genes with disease."

He said that roughly half of Amgen's current research projects are influenced directly by genetics, and of those, at least 90% stems from the work happening at deCODE.

Stefansson added that this small but mighty country is making a significant mark on the field. "We have probably made as much contribution as the rest of Europe put together," he said.

However, not everyone agrees with what deCODE is doing.

More than 150,000 people have donated their blood samples to the project.

Many critics have raised questions about privacy and what will be done with this information, as well as teams having access to the population's medical records. In response, Stefansson highlighted that all the data at deCODE are encrypted and anonymous.

"It's a really important project," said Dr. Frances Williams, a genetic epidemiologist at Kings College London. "It's got great buy-in from the population who volunteered their samples to the project."

But Williams added that when investigating something as personal as someone's DNA, clarity in terms of how this insight will be used and researched is crucial among those volunteering their blood. "You've got to be clear with volunteers on what exactly you're offering," she said.

Controversially, Stefansson hopes that the need for anonymity will soon change.

Removing anonymity

"We have insight into the genome of all Icelanders today," he said. "And one of the big questions is, 'How can society take advantage of it?' There are some obstacles that society has to get over before it will use it."

He offers an example: There is just one mutation of BRCA2 -- a breast cancer gene -- in Iceland. Only 0.8% of the Icelandic population carries it, but of those women, there is an 86% probability of developing potentially lethal cancer.

"We can, at the push of a button, find encrypted ID of all these carriers," Stefansson said. "If society would want to use this, they could find these women, they could approach them, and they could mitigate most of this risk."

But, he added, "for the moment, society is struggling with whether or how to use this. One of the concerns ... is that by approaching these women, you would be violating their right now to know. However, it has been a tradition in our society, like many others, that you don't let people die prematurely if you can save their lives."

Williams believes this will become problematic. "Different people have different views on whether or not they want to know about that," she said. "It's not for scientists to second-guess what people want to know."

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She acknowledged that, in the case of the BRCA genes, knowledge could be used to help reduce someone's risk of developing breast cancer through a mastectomy. But other genes are less clear, and knowledge of risk may not always come with an option to reduce it.

For now, Stefansson hopes that cracking the code of our genetics could lead to life-saving knowledge and medicines.

Trials are underway on drugs based on the Alzheimer's variant deCODE discovered, as well as a new cardiovascular drug.

"It has always been considered a virtue in our culture to know as much about yourself as possible," Stefansson said. "I don't think that there is any exception for genetics. We just want to know who we are."